High voltage MOS transistors are semiconductor devices that can operate with high terminal voltages. High-voltage integrated circuits (ICs) that include high voltage MOS transistors are widely used in applications for the automobile industry, display drivers, portable telecommunication devices, medical equipment, and other areas. As an example, high voltage (e.g., greater than 20 volts) MOS transistors are integrated into a gate driver IC to deliver display signals to a liquid crystal display (LCD) panel. However, with the continuous process shrinking in advanced technology, breakdown voltages of these high voltage MOS transistors are also reduced. In addition, in order to increase saturation current of a high voltage MOS transistor, the on-resistance would be reduced, thereby the breakdown voltage of the high voltage MOS transistor would be reduced as well. It is desirable to increase saturation current of a high voltage MOS transistor without reducing the breakdown voltage of the high voltage MOS transistor.
Like reference symbols in the various drawings indicate like elements.